From Imitation of Christ:
We should enjoy much peace if we did not concern ourselves with what others say and do, for these are no concern of ours. How can a man who meddles in affairs not his own, who seeks strange distractions, and who is little or seldom inwardly recollected, live long in peace?
Blessed are the simple of heart for they shall enjoy peace in abundance.
Why were some of the saints so perfect and so given to contemplation? Because they tried to mortify entirely in themselves all earthly desires, and thus they were able to attach themselves to God with all their heart and freely to concentrate their innermost thoughts.
We are too occupied with our own whims and fancies, too taken up with passing things. Rarely do we completely conquer even one vice, and we are not inflamed with the desire to improve ourselves day by day; hence, we remain cold and indifferent. If we mortified our bodies perfectly and allowed no distractions to enter our minds, we could appreciate divine things and experience something of heavenly contemplation.
The greatest obstacle, indeed, the only obstacle, is that we are not free from passions and lusts, that we do not try to follow the perfect way of the saints. Thus when we encounter some slight difficulty, we are too easily dejected and turn to human consolations. If we tried, however, to stand as brave men in battle, the help of the Lord from heaven would surely sustain us. For He Who gives us the opportunity of fighting for victory, is ready to help those who carry on and trust in His grace.
If we let our progress in religious life depend on the observance of its externals alone, our devotion will quickly come to an end. Let us, then, lay the ax to the root that we may be freed from our passions and thus have peace of mind.
If we were to uproot only one vice each year, we should soon become perfect. The contrary, however, is often the case — we feel that we were better and purer in the first fervor of our conversion than we are after many years in the practice of our faith. Our fervor and progress ought to increase day by day; yet it is now considered noteworthy if a man can retain even a part of his first fervor.
If we did a little violence to ourselves at the start, we should afterwards be able to do all things with ease and joy. It is hard to break old habits, but harder still to go against our will.
If you do not overcome small, trifling things, how will you overcome the more difficult? Resist temptations in the beginning, and unlearn the evil habit lest perhaps, little by little, it lead to a more evil one.
If you but consider what peace a good life will bring to yourself and what joy it will give to others, I think you will be more concerned about your spiritual progress.
[resources: Imitation of Christ]